SYNTHESIS, STRUCTURE AND THERMAL-DECOMPOSITION OF TETRA(2-PYRIDYL)PYRAZINE-CENTER-DOT-I-2 CHARGE-TRANSFER COMPLEXES

In both the solid state and in solution, 2,3,5,6-tetrakis(2'-pyridyl)p yrazine (tpp) reacts with iodine to form charge-transfer complexes. Th e solid state process results in the exclusive production of a mono-I- 2 adduct, 3, while the solution reaction can produce both 3 and a bis- I-2 adduct, 4. The X-ray crystal structure of 4 is described and a str ucture for 3 is proposed based upon spectroscopic evidence and molecul ar orbital calculations. The thermal decompositions of 3 and 4 proceed by I-2 evolution at very different rates and lead to different polymo rphs of tpp. The mechanism of this process is described in terms of so lid state reaction theory.